Process of seasoning steel articles



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-' citizen of the United States, residing at Hartford, in the county ofHartford and State of Connecticut, have invented certain new and usefulImprovements in Processes of Seasoning Steel Articles, of which thefollowing is a specification.

It is a recognized fact. that there is a marked tendency for small steelarticles which have been hardened to vary in shape or size, eitherby'warping or distortion or by expansion or contraction. Suchdistortions or variations are ordinarily relatively small and they takeplace slowly, frequently gage blocks or other. articlesaftenhavingcontinuing over a period of months or even i of years. .F or certainclasses of work these dlstortlons or varlatlons are so small as to beimmaterial, but in work involving high precision the distortions orvariations are large enough toseriously interfere with the accuracyrequired.

Distortions'or variations such as above referred to are particularlydetrimental in the case of dimension gage blocks which are made withopposite parallel flat end faces at predetermined distances apart, theblocks being-furnished in sets with diflerentlengths so that bycombining or selecting difierent blocks any desired dimension within therange of the set can be secured. It is now possible to make blocks ofthis class so that the maximum error in each block from the nominal sizethereof is not more than five millionths of an inch and is he uently aslow as one millionth of 'an inch. en ,accuracy of this order isattainable the matter of distortion or variation from the form and sizeof the block as originally made is of vital importance. It has beenfound that gage blocks that are initially accurate within the limitsspecified may after a period of some weeks or months have become sodistorted or changed in shape or size as to have errors far in excess ofthe allowable maximum.

It is well known that these distortions or variations gradually diminishin extent, the steel slowly approachin a permanent condition, whichcondition however ma not be fully attained until after a period 0 monthsi or even of years following hardening. It

appears that a certain natural seasoning 0 eration takes place,probablyassisted by t e Specification of Letters Patent.

Application filed May 13, 1920. Serial No. 881,188.

PROCESS OF SEASONING STEEL ARTICLES.

weather conditions, and probably further as Patented Apr. 5, 1921.

sisted by the shocks and vibrations to which an article is subjectedduring use.

Ord 1nar1ly it is notpractical to rely upon this natural seasoninoperation because of the longtime required and the objectof the presentmvention is to provide a process of seasoning which is capable ofsecuring the same or, substantially the same permanency that as securedby natural seasoning but which is capable of-being carried out in arelatively short period of time. In accordance with the invention thesteel ordinarily from 300 to 450"F.. In any case it is preferably ashigh as can be used for the particular steel wlthout softening'it to anobjectionable extent. The predetermined temperature having been reachedthe oil with the blocks therein is maintained at this temperature for adefinite period, preferably about one to eight hours. For one grade ofsteel used for gage blocks it has been found that a temperature of 400maintained for eight hours gives satisfacto results. At the end of theheating perio the oil bath with the blocks still therein is allowed toslowly return to normal temperature.- After the blocks are removed fromthe oil bath they are subjected to a large number of alternate dips inhot and cold' baths. The hot and cold baths have temperaturesrespectively somewhat above and below the normal temperature.Preferably. the hot bath is of oil, the temperature of which ismaintained at about 250 to 285 F. Preferably the cold bath is ofkerosene, the temperature of which is maintained at about 0 to -20 F.The. blocks are dipped alternately intothe hot oil and into the coldoil, being allowed to remain in each long enough to attain thetemperature of the I themselves and thus relieve the stresses Set up bythe hardening operation;

.The vibration may be effected 1n any de- 'sired way, as, for instance,by mounting the gages or other articles in a suitable frame and bysubjecting the frame to the actlon of a pneumatic hammer.

As the result of the foregoing treatment the blocks or other articleshave within a short time been causedto undergo those distortions orvariations which would otherwise have been distributed over a period ofmonths or years. Theblocks or other articles are in substantiallypermanent form and are ready to be subjected to final grinding orlapping operations whereby they are made accurate within the limitsrequired.

What I claim is:

1; The herein described process of seasoning steel articles afterhardening, which consists in placing the articles in a liquid bath,

slowly heating the bath with the articles to a relatively hihtemperature, permitting the bathYwit the articles to slowly cool tonormal temperature, and then alternately dipping the articles a largenumber of times in hot and cold baths at temperatures respectively aboveand below the normal. temperature.

2. The process as described in claim 1 in which the initial'bath isheated to a temperature as high as is possible without objectionablysoftening the steel.

3. The process a described in claim 1 in memes which the initial bath isheated to a temwhich the initial bath is maintained at its maximumtemperature for a considerable period of time.

5. The process as described in claim 1 in which the initial bath ismaintained at its maximum temperature for a period of from one to eighthours.

6. The process as described in claim 1 in which the temperatures of thehot and cold "baths are respectively from 250 to 285 F.

and from O to 20 F.

7. The process as described in claim 1 in which the articles are dippedapproximately seventytime in each of the last said baths.

8? The herein described process of seasoning steel articles afterhardening, which consists in placing the articles in a liquid bath,slowly heating the bath with the articles toa temperature from 300 to450 F, maintaining the bath with the articles at the said temperaturefor a period of approximately from one to eight hours, permitting thebath with the articles to slowly cool to normal temperature, and thenalternately dipping the articles approximately seventy times in hot andcold baths at temperatures respectively from 250 to 285? F. and from 0to ,,--20"- F.

9. The process as described in claim 1 in which the articles arevibrated during at least a part of the process steps specified.

10. The process as described in claim 1 in which'the articles arevibrated while in the initial high. temperature bath.

11. The process as described in claim 1 in BRYANT H. BLOOD.

